A class of imprintable, bendable, and shape-conformable polymer electrolyte with excellent electrochemical performance in a lithium battery system is reported. The material consists of a UV-cured polymer matrix, high-boiling point liquid electrolyte, and Al2 O3 nanoparticles, formulated for use in lithium-ion batteries with 3D-structured electrodes or flexible characteristics. The unique structural design and well-tuned rheological characteristics of the UV-curable electrolyte mixture, in combination with direct UV-assisted nanoimprint lithography, allow the successful fabrication of polymer electrolytes in geometries not accessible with conventional materials.

Polyethylene glycol (PEG) has been coupled to many cationic polymers such as polyethylenimine (PEI) to improve the stability and transfection efficiency. We prepared PEG-grafted PEI with different lengths and amounts of PEG and used these graft copolymers as nonviral gene vectors. We measured the complex size and zeta-potential of polymer-DNA complexes in the presence of salt to estimate the stability of polymer-DNA complexes. We also investigated the cytotoxicity and transfection efficiency in C3 cells. In the case of graft copolymers, the stability of polymer-DNA complexes and transfection efficiency were affected by the graft length and amount of PEG side chain. PEG side chains stabilize the polymer-DNA complexes in the presence of salt, but the longer PEG side chains also interrupt the gene delivery in the cells due to the more efficient steric hindrance by longer PEG side chains, and therefore the transfection efficiency is decreased. Short PEG side chains with molecular weight of 350 kDa stabilized the polymer-DNA complexes without decreased transfection efficiency.

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A highly adhesive and thermally stable copolyimide (P84) that is soluble in organic solvents is newly applied to silicon (Si) anodes for high energy density lithium-ion batteries. The Si anodes with the P84 binder deliver not only a little higher initial discharge capacity (2392 mAh g(-1)), but also fairly improved Coulombic efficiency (71.2%) compared with the Si anode using conventional polyvinylidene fluoride binder (2148 mAh g(-1) and 61.2%, respectively), even though P84 is reduced irreversibly during the first charging process. This reduction behavior of P84 was systematically confirmed by cyclic voltammetry and Fourier-transform infrared analysis in attenuated total reflection mode of the Si anodes at differently charged voltages. The Si anode with P84 also shows ultrastable long-term cycle performance of 1313 mAh g(-1) after 300 cycles at 1.2 A g(-1) and 25 °C. From the morphological analysis on the basis of scanning electron microscopy and optical images and of the electrode adhesion properties determined by surface and interfacial cutting analysis system and peel tests, it was found that the P84 binder functions well and maintains the mechanical integrity of Si anodes during hundreds of cycles. As a result, when the loading level of the Si anode is increased from 0.2 to 0.6 mg cm(-2), which is a commercially acceptable level, the Si anode could deliver 647 mAh g(-1) until the 300th cycle, which is still two times higher than the theoretical capacity of graphite at 372 mAh g(-1).

A stable electrolyte system at a charge voltage over 4.5 V is the key to successfully obtaining higher energy density by raising the charging cutoff voltage. We demonstrate a fluorinated electrolyte (1 M LiPF 6 fluoroethylene carbonate (FEC) and methyl (2,2,2-trifluoroethyl) carbonate (FEMC) (FEC/FEMC = 1/9, v/v)) for a high-voltage LiNi 0.5 Mn 0.3 Co 0.2 O 2 /graphite system. The stability of the fluorinated electrolyte for the LiNi 0.5 Mn 0.3 Co 0.2 O 2 (NMC532) cathode was investigated using scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy. The charge-discharge performance of the fluorinated electrolyte was superior to the corresponding non-fluorinated electrolyte system at a charging cutoff voltage of 4. Considerable efforts have been made for developing high-charge voltage platforms that provide large capacities, thereby helping improve the energy density of lithium-ion batteries (LIB). Because electrical energy is the product of the discharge capacity and the average discharge voltage, it is important to search for cathode materials with a high discharge voltage.1 To this end, many studies have been devoted to improving cathode materials for high-voltage applications, such as polyanion oxides (LiCoPO 4 ), spinel-type oxides (LiMn 2 O 4 ), and layered oxides (LiNi x Mn y Co 1-x-y O 2 ). Among cathode materials, LiNi 0.5 Mn 0.3 Co 0.2 O 2 (NMC532) is one of the most promising for its potential practical application in high-voltage lithium-ion battery. 2-4However, there remains a critical obstacle that should be overcome for high-voltage lithium-ion batteries. Oxidative instability of the conventional non-aqueous electrolyte takes place at a charging voltage beyond 4.5 V, leading to severe decay of cycling performances.5 Per research, practical approaches to improving performance for highvoltage operation include use of a new solvent or introducing functional additives to the electrolyte. [6][7][8] Recently, incorporation of the fluorinated compound either as solvent or as additive have been investigated for high-voltage LIB and positive effects have been reported. [9][10][11][12][13] Especially, utilization of fluoroethylene carbonate (FEC), which is well known to form solid-electrolyte interphase (SEI) on the anode surface with the small amounts addition, in high-voltage LIB has gathered attention. Based on 1 M LiPF 6 ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (EC/EMC = 3/7, wt/wt) electrolyte, FEC was used as a fluorinated solvent (20∼50%) to replace EC or as a fluorinated additive (>5%) in a base electrolyte solution. However, there are a few studies reported on the electrolyte system consisting of wholly fluorinated solvents and additive. Here, we demonstrate a fully fluorinated electrolyte system composed of FEC and methyl (2,2,2-trifluoroethyl) carbonate (FEMC) at a volume ratio of 1:9 for high-voltage lithium-ion batteries. Amount of FEC is selected slightly higher than the case of FEC as additive in base solvent and much lower th...